The present invention relates to a safety protection structure for aquarium heater, which is able to protect the heater from leakage of electricity, blowing up due to abruptly increasing temperature after separated from the water and burning of environmental articles by over-heated surface of the heater after separated from the water.
It is known that it is important to properly keep constant the water temperature in an aquarium. Effective temperature control can avoid disease or death of water fowl. A conventional heater is widely used to heat the water in an aquarium. Such heater includes a heating coil and a bimetal heating circuit which are received in a glass test tube. The activation time of the heating coil is controlled by means of adjusting the contact distance of the bimetal plate. In the case of over-low water temperature, the heating coil is automatically activated to heat the water. Many kinds of improved aquarium heaters have been developed. However, all these devices can only provide an approximate temperature and can hardly accurately control the temperature. This is insufficient for some specific aquariums. Therefore, a thermostat has been developed, which via electronic technique more accurately detects temperature and controls the heating time. The thermostat is composed of an independent temperature controlling circuit and an independent heater. FIG. 1 shows a conventional heater in which a mica plate is placed at the center of the heating coil to separate two halves of the heating coil. The heating coil with the mica plate is positioned in a quartz tube which is high temperature-resistant. The interior of the quartz tube is filled with magnesium oxide and sealed at one end by a cap to avoid oxidation of the heating coil and conduct the heat. The heating wire is extended out from the other end which is sealed by a cap. Such structure can achieve an excellent heating effect to efficiently increase the water temperature in the aquarium. However, in use, it should be particularly noted that a protective housing must be fitted around the heater. Otherwise, the high temperature of the surface of the heater is very likely to bum the water fowl in the aquarium. In addition, the conventional heater has some shortcomings in operation as follows:
1. In use, the heater must be kept immersed in the water. In case the heater is moved from the water in a heating state, the temperature will abruptly increase. If the heater is then again placed into the water, the difference in temperature of inner and outer sides will lead to cracking fissures of the heater. The fissures are normally extremely fine and can be hardly seen. However, the water can infiltrate through the fissure to cause leakage of electricity and danger of shock.
2. In the case that the heater is cracked and moved from the water in a continuously heating state, the water accumulating in the heater will be vaporized to blow up and damage the heater.
3. After the heater is separated from the water, the externally added electronic sensor fails to detect such situation in time and the heater will continuously heat. As a result, the temperature of the surface of the heater will very soon reach over 200.degree. C. This often leads to burning of environmental articles and fire accident.